There are many factors that contribute to the final construction cost of any project; size, complexity, and finishes being just a few. Every site has different constraints and every client has different requirements.
There are literally 1000’s of parameters and decisions that need to be considered in any project and every decision will impact the cost in some way. However most projects can be estimated using a rate per sqm rule of thumb. So depending on the nature of the works, be it structural or just decorative, you can start to build a reasonable estimate.
Extension normally cost between £2000-£3000/sqm for the building work, to which you need to add a few additional premium items such as a kitchen if applicable, along with professional fees and VAT.
We have put together a reasonably sophisticated cost calculator which will use rates per sq m to help you estimate your project cost.
It is free and will give you a really good starting point from where to consider your project. Click to access the MWA Project Cost Estimator